Pending U.S. patent application Ser. No. 304,093 in the name of Mahoney and Benwood, shows an apparatus and method for making multicolor toner images using four drums and an intermediate transfer web. In one embodiment the four drums are each separate photoconductive imaging members which create different color toner images which are transferred in registration to the intermediate transfer member to create a multicolor image which is then transferred to a receiving sheet in a single step. In a second embodiment each drum is covered with a xeroprinting master each of which create different color toner images which are transferred in registration to the intermediate transfer member. U.S. Pat. No. 4,232,961 also shows separate photoconductive imageing members for four color toners including transfer to an intermediate transfer member.
A number of other references show parallel processes in which the images are transferred from separate photoconductors to a receiving sheet, see for example U.S. Pat. No. 4,690,542; U.S. Pat. No. 4,662,739; U.S. Pat. No. 4,803,515; U.S. Pat. No. 4,162,843; U.S. Pat. No. 4,796,050; U.S. Pat. No. 4,664,501; and U.S. Pat. No. 4,752,804. U.S. Pat. No. 4,835,570 shows manual application of xeroprinting masters to a series of drums which are used to make multicolor images for transfer directly to a receiving sheet.
All of these parallel processes have the advantage of making multicolor images at roughly the same speed that a single color image can be made on each individual drum. This is a substantial improvement in speed over the present commercial electrophotographic color systems in which color toner images are made consecutively on the same imaging member.
However, the above disclosures which show separate photoconductive members require separate imaging stations and sensitive materials for each color. The structures which use masters require separate apparatus for forming the master images. The masters are generally applied to the drums by hand. Registration of the colors making up the multicolor image from masters is dependent upon the accuracy of forming the separate masters and their placement on the drums. These are serious sources of registration error.